---brokenrabbits.nlogo

NETLOGO

globals [ ticks ]
breeds [ sheep wolves rabbits]
turtles-own [ energy ]
sheep-own [ grabbed? ]     ;; used to prevent two wolves from eating the same sheep
rabbits-own [ grabbed? ]     ;; used to prevent two wolves from eathing the same rabbit
patches-own [ countdown ]

to setup 
  ca
  set ticks 0
  ask patches [ set pcolor green ]
  if grass? [
      ;; indicates whether the grass switch is on  
      ;; if it is true, then grass grows and the sheep eat it  
      ;; if it false, then the sheep don't need to eat  
    ask patches [
      set countdown random grass-regrowth-time ;; initialize grass grow clocks randomly
      if (random 2) = 0  ;;half the patches start out with grass
          [ set pcolor brown ]
    ]
  ]

  set-default-shape sheep "sheep"
  create-custom-sheep initial-number-sheep  ;; create the sheep, then initialize their variables
  [ 
    set color white
    set label-color blue - 2
    set energy random (2 * sheep-gain-from-food)
    setxy random screen-size-x random screen-size-y
    set grabbed? false
  ] 
   
  set-default-shape wolves "wolf"
  create-custom-wolves initial-number-wolves  ;; create the wolves, then initialize their variables
  [ 
    set color black
    set energy random (2 * wolf-gain-from-food)
    setxy random screen-size-x random screen-size-y
  ]

  set-default-shape rabbits "bunny"
  create-custom-rabbits initial-number-rabbits  ;; create the wolves, then initialize their variables
  [ 
    set color yellow
    set energy random (2 * rabbit-gain-from-food)
    setxy random screen-size-x random screen-size-y
  ]

  display-labels
  
  do-plot
end

to go
  ask sheep [
    move
    if grass? [
      set energy energy - 1  ;; deduct energy for sheep only if grass? switch is on
      eat-grass
    ]
    reproduce-sheep
    death
  ] 
  ask wolves [
    move
    set energy energy - 1  ;; wolves lose energy as they move
    catch-sheep  
    if (initial-number-rabbits > 0 ) [
       catch-rabbits 
    ]   
    reproduce-wolves
    death  
  ]
  
  if (initial-number-rabbits > 0 ) [
  ask rabbits [
     move
     if grass? [
        set energy energy - 1 ;; 
        eat-grass
     ]
     reproduce-rabbits
     death 
   ]
   ]  
  if grass? [ ask patches [ grow-grass ] ]
  do-plot  ;; plot populations
  every 0.5
    [ display-labels ]
  set ticks ticks + 1
  if not any turtles [ stop ]
end

to move  ;; turtle procedure
  rt random 50 - random 50
  fd 1 
end

to eat-grass  ;; sheep procedure
  ;; sheep eat grass, turn the patch brown
  if pcolor = green [ 
    stamp brown 
    set energy energy + sheep-gain-from-food  ;; sheep gain energy by eating
  ] 
end

to reproduce-sheep  ;; sheep procedure
  if random 100 < sheep-reproduce [  ;; throw "dice" to see if you will reproduce
    set energy (energy / 2)          ;; divide energy between parent and offspring
    hatch 1 [ rt random 360 fd 1 ]   ;; hatch an offspring and move it forward 1 step
  ]
end
 
to reproduce-rabbits  ;; sheep procedure
  if random 100 < rabbit-reproduce [  ;; throw "dice" to see if you will reproduce
    set energy (energy / 2)          ;; divide energy between parent and offspring
    hatch 1 [ rt random 360 fd 1 ]   ;; hatch an offspring and move it forward 1 step
  ]
end
 
to reproduce-wolves  ;; wolf procedure
  if random 100 < wolf-reproduce [  ;; throw "dice" to see if you will reproduce
    set energy (energy / 2 )  ;; divide energy between parent and offspring
    hatch 1 [ rt random 360 fd 1 ]  ;; hatch an offspring and move it forward 1 step
  ]
end

to catch-sheep  ;; wolf procedure
  locals [prey]
  set prey random-one-of sheep-here             ;; grab a random sheep
                           with [not grabbed?]  ;; that no one else is grabbing
  if prey != nobody                             ;; did we get one?  if so,     
    [ set grabbed?-of prey true                 ;; prevent other wolves from grabbing it
      ask prey [ die ]                          ;; kill it
      set energy energy + wolf-gain-from-food ]     ;; get energy from eating
end

to catch-rabbits  ;; wolf procedure
  locals [prey]
  set prey random-one-of rabbits-here             ;; grab a random sheep
                           with [not grabbed?]  ;; that no one else is grabbing
  if prey != nobody                             ;; did we get one?  if so,     
    [ set grabbed?-of prey true                 ;; prevent other wolves from grabbing it
      ask prey [ die ]                          ;; kill it
      set energy energy + wolf-gain-from-rabbit ]     ;; get energy from eating
end


to death  ;; turtle procedure
  ;; when energy dips below zero, die
  if energy < 0 [ die ] 
end

to grow-grass  ;; patch procedure
  ;; countdown on brown patches, if reach 0, grow some grass
  if pcolor = brown [ 
    ifelse countdown <= 0
      [ set pcolor green
        set countdown grass-regrowth-time ] 
      [ set countdown (countdown - 1) ] 
  ] 
end

to do-plot 
  set-current-plot "populations"
  set-current-plot-pen "sheep" 
  plot count sheep 
  set-current-plot-pen "wolves"
  plot count wolves
  if grass? [
    set-current-plot-pen "grass / 4"
    plot count patches with [ pcolor = green ] / 4  ;; divide by four to keep it within similar
                                                ;; range as wolf and sheep populations
  ]
end

to display-labels
  ifelse show-energy?
  [
    ifelse grass?
    [
      ask turtles
      [ set label round energy ]
    ]
    [
      ask wolves
      [ set label round energy ]
      ask sheep
      [ set label no-label ]
    ]
  ]
  [
    ask turtles
    [ set label no-label ]
  ]
end


; *** NetLogo Model Copyright Notice ***
;
; This model was created as part of the project: CONNECTED MATHEMATICS:
; MAKING SENSE OF COMPLEX PHENOMENA THROUGH BUILDING OBJECT-BASED PARALLEL
; MODELS (OBPML).  The project gratefully acknowledges the support of the
; National Science Foundation (Applications of Advanced Technologies
; Program) -- grant numbers RED #9552950 and REC #9632612.
;
; Copyright 1998 by Uri Wilensky. All rights reserved.
;
; Permission to use, modify or redistribute this model is hereby granted,
; provided that both of the following requirements are followed:
; a) this copyright notice is included.
; b) this model will not be redistributed for profit without permission
;    from Uri Wilensky.
; Contact Uri Wilensky for appropriate licenses for redistribution for
; profit.
;
; This model was converted to NetLogo as part of the project:
; PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN
; CLASSROOMS.  The project gratefully acknowledges the support of the
; National Science Foundation (REPP program) -- grant number REC #9814682.
; Converted from StarLogoT to NetLogo, 2000.  Updated 2002.
;
; To refer to this model in academic publications, please use:
; Wilensky, U. (1998).  NetLogo Wolf Sheep Predation model.
; http://ccl.northwestern.edu/netlogo/models/WolfSheepPredation.
; Center for Connected Learning and Computer-Based Modeling,
; Northwestern University, Evanston, IL.
;
; *** End of NetLogo Model Copyright Notice ***

@#$#@#$#@
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SWITCH